On this board, 6C is completely cold and should be the top spot (rather than scoring 3/10). Also, 6D will usually make and should receive a nonzero score (but not as good as 6C).

Both 7C and 7NT require a favorable lead to make. However, as long as hearts are not lead they will make. They should probably receive nonzero scores (but low ones).

3NT will sometimes fail (can lose five heart tricks) and is obviously lower scoring than 6C making. Rather than being the top spot, this should be somewhere below 6D (but above the grand slams and 6NT). I would recommend: